Formula to warn end date coming up

Hello, this is my first post.
I have searched endlessly and can not find the formula to have a cell change colour when the end date is arriving.
For example - I have a document that expires after one year. I would like to set a formula so that the cell turns amber a month before its due date and red on the day it expires.

I am using Office 2010.

Any/all help is appreciated.